Because of their high energy efficiency, light fixtures with light-emitting diodes as light source (so-called LED retrofit lamps) are growing in popularity as a replacement for conventional light fixtures such as halogen or incandescent lamps. In contrast to conventional light fixtures, however, the light generated by light-emitting diodes usually does not cover the entire solid angle homogeneously. However, the generated radiation profile can be adapted by suitable optical units. As a result, in particular, LED spot lights can be provided which emit at a defined and in particular relatively narrow emission angle.
Currently available LED spot lights typically have an emission angle in the region of below 40°. This enables efficient illumination of individual regions in the room, but illumination of a complete room with such low emission angles can only be achieved with difficulty. Moreover, LED spot lights exist which have relatively large emission angles of 100° or 120°. Such LED spot lights with a large emission angle have the advantage that complete rooms can be illuminated by them. However, only relatively little light is emitted downwards, where the light is most required for illumination.
A good compromise between a large surface area illumination and a local illumination can be achieved with an emission angle in the range of at least 50° and at most 80°, in particular at least 55° and at most 70°. However, already existing optical units, with which such an emission angle can be produced, have a low optical efficiency. The optical efficiency is the ratio of the light of the light fixture emitted in a 90° cone according to the EU Directive No. 1194/2012 of Dec. 12, 2012 and the entire light emitted by the light fixture. However, in the design of an optical unit, the spatial dimensions for improvement of the optical efficiency cannot be selected arbitrarily. Advantageously, the optical unit is configured so that it can be introduced into an existing socket, so that compatibility with existing lights is guaranteed.